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Paul Leyland

The photometry tools which run everywhere and with which I have some familiarity are APT, AstroImageJ and IRAF/DAOPHOT.  Those are the ones which I will target.  AIJ will be familiar to many here; I’m climbing its learning curve with the assistance of the excellent BAA-VSS guide.  As noted above, I like APT.  DAOPHOT is the grand-daddy from which most other tools have been developed, including munipack/muniwin (another excellent tool but not one with which I’m currently playing).

DAOPHOT is a real professional’s tool.  I’ve scripted it to analyze approximately 10k images taken over the last several months by Kevin Hills.  It’s a refugee from the 1980s and doesn’t fit particularly well with the GUI paradigm.  I’m an old fogey so that doesn’t worry me too much.  What I really like is that although it uses only circular apertures, the star PSF is evaluated directly  from the data (that is it doesn’t assume any particular shape and so can handle trailed or otherwise munged images) and can vary from point to point in the image.  Coupled with very effective de-blending of closely neighboring stars, it gives very accurate results even in very crowded fields.

As far as I can tell (please correct me if I’m wrong) AIJ employs only circular apertures and assumes that the star images are circularly symmetrical.  If so, a trailed star has to be included inside a relatively large circular aperture and so encloses rather a lot of sky as well, leading to poorer estimates for the magnitude and its error.

APT (again, AFAICT) doesn’t allow for a spatially-varying PSF but does allow apertures which are ellipses of arbitrary orientation.  As well as modelling non-circular stars nicely, this also fits well with the requirements for performing photometry of galaxies (and perhaps comets?).

Software written so far will parse a downloaded AAVSO CCD photometry file and produce target lists for APT and a RADec file for AIJ.  Still to come is code which replicates the BAA-VSS Excel spreadsheets which (again, AFAICT) run only on MS Office.

Code to drive IRAF/DAOPHOT and Munipack is likely to take some time because I’m probably only the person interested in them

To early to ask for beta testers but your time will come!